1. Technical Field
This disclosure relates generally to an automated process and method to control pump motor speed over time to cause the actual fluid level in a vessel or well bore to track a computer generated fluid level curve over time to a selected target fluid level above the pump, and to maintain that level over time regardless of varying conditions that may result from reservoir depletion, pump wear conditions, and or other fluctuations such as fluid rate entering a vessel.
2. Background
Methods of pumping fluid from vessels or wellbores have and continue to evolve. Pump protection methods and automation for pump operations exist and continue to improve.
Operators of these systems have encountered a common experience that destroys the artificial lift system namely, dry pumping (also called “pumping off”). Many have attempted ways to intuitively determine ways to protect the pumping equipment creating pump-off control devices that use a PLC (Programmable Logic Controller) with sensors to stop the pump when it is observed that there is no fluid flow at the surface or coming to or from the pump.
Operators use many monitors to help with dry pumping protection such as flow rate meters at the surface which are used to compare against expected flow rates, or electric motor operating parameters such as amperage load and capacitance of fluid, as well as other mechanical observations such as vibration and pounding that leads to damage of operational equipment. Through all these monitoring methods, the idea is to protect the pump if the estimate of flow rate is incorrect and ultimately stop the pump when the pump runs out of fluid to pump.
Prior art (pump off control or intuitive speed control) systems require time consuming step ladder programming in setting up a standard PLC to establish operational parameters and then set limits which as time passes, require further human intervention to “tune” the operation as the operator determines over time that the speed of operation they select to pump at desired rates was an incorrect guess.
Other art specific to electric submersibles and or progressive cavity pumps seek to enhance or maximize production. This automation is based on estimating an expected fluid flow rate and comparing the expected to the actual flow rate to determine pump speed. This is simply pumping faster to get more fluid flow.
What is needed is a pump control system that does not need to know pump output potential at a given speed in order to perform its given task and does not have to take into account pump flow design rates. Also, such a system should be able to control all forms of artificial lift systems that employ an electric motor as the prime mover of the pump.
Preferably, such a system should require no human effort once the operator provides two inputs: desired fluid level target and the time or number of days they wish the processor to achieve the target. After defined, no additional input should be required, regardless of changing reservoir and pump conditions over time; the system should continuously calculate and provide speed control commands to offset changing conditions.